The present invention relates generally to optical assemblies and, more particularly, to an optical assembly having an optical device and a lens wherein the optical device is spaced a distance from the optical axis of the lens.
An optical assembly uses a lens to focus light associated with an optical device. The optical device may, as examples, be a light source or a photosensor. When the optical device is a light source, the optical assembly may serve as an illuminator in which the lens focuses light emitted by the light source onto an object. When the optical device is a photosensor, the optical assembly may serve is an imaging device in which the lens focuses light reflected from the object onto the photosensor to generate an image of an object. Optical assemblies may be used in a variety of applications, such as electronic scanners and bar code readers, to illuminate objects and to generate images of objects.
Bar codes are used in numerous applications to identify objects to which the bar codes are affixed. Examples of bar codes include the uniform price code used to identify retail goods and various forms of shipping labels used to track parcels. A bar code is an optical symbol containing coded information, in which the symbol is able to be imaged by an imaging device. The imaging device generates an image of the bar code and converts the image to machine-readable image data, referred to herein simply as xe2x80x9cimage data.xe2x80x9d The image data is output to a processor, which deciphers the image data representing the bar code to xe2x80x9creadxe2x80x9d the bar code. Reading the bar code is the operation of deciphering the bar code to obtain the information encoded in the bar code. The information encoded in the bar code may, as an example, identify the object to which the bar code is affixed.
A bar code may, as an example, be a representation of a character set, e.g., ASCII characters represented by binary numbers. One type of bar code format that represents a binary number consists of an array of alternating reflective and nonreflective surfaces in which the transition from one surface to an adjacent surface represents the transition from one bit to another bit of a binary number. The alternating reflective and nonreflective surfaces may, for example, be alternating reflective and nonreflective stripes. The reflective stripes are sometimes referred to herein as spaces and the nonreflective stripes are sometimes referred to herein as bars. The bars may, as an example, be dark-colored stripes and the spaces may, as an example, be light-colored stripes. Each stripe, thus, represents one bit of the binary number. The stripes may, as an example, be either wide or narrow. A wide stripe may represent a one and a narrow stripe may represent a zero. The binary number represented by the bar code is, thus, defined by the widths of the alternating bars and spaces.
The array of alternating bars and spaces in the bar code format described above has numerous different specifications that may apply to the format. The specifications define the numbers of, and widths of, the bars and spaces used to represent the characters used in the format. These specifications also define the reflectivity of the bars and spaces for the various formats. Other bar code formats, may, as examples, comprise two-dimensional arrays of reflective and nonreflective areas or concentric reflective and nonreflective circles. All the bar codes, however, have reflective and nonreflective surfaces.
A bar code reader is a photoelectric device that is used to xe2x80x9creadxe2x80x9d bar codes. Reading a bar code is the process of analyzing the areas of high and low reflectivity to decipher the information encoded in the bar code. The bar code reader typically comprises an illuminator, an imaging device, and a processor. The illuminator serves to illuminate the bar code via an illumination beam of light. The illuminator may, for example, be a laser or an array of light-emitting diodes. An image beam of light constituting an image of the bar code reflects from the bar code. The imaging device receives the image beam and converts the image of the bar code to image data. The processor analyzes the image data to distinguish the image data representing the reflective spaces from the image data representing the nonreflective bars. Based on the analysis of the image data, the processor is able to decipher the information encoded in the bar code.
The imaging device uses a photosensor, such as a charge-coupled device, often referred to herein simply as a CCD, to convert the image beam to image data. A CCD typically consists of at least one linear array of photodetector elements, referred to herein simply as photodetectors, mounted to a substrate, or etched into a wafer, e.g., a silicon wafer used in semiconductor fabrication. A CCD may, as an example, comprise approximately 2,700 photodetectors in the array wherein the individual photodetectors have a width of approximately 11 microns, thus, making the array approximately three centimeters long and 11 microns wide. The high concentration of photodetectors in the array typically allows a single CCD to image a bar code as described above with enough precision to determine the widths of the reflective and nonreflective surfaces. The CCD typically images a very narrow xe2x80x9cscan linexe2x80x9d portion of the bar code wherein the scan line transverses the stripes comprising the bar code. The scan line is generally as narrow as the array of photodetectors, e.g., 11 microns.
The illuminator should uniformly illuminate the bar code; otherwise, the processor may be unable to distinguish the reflective areas from the nonreflective areas. For example, if one end of the bar code is more intensely illuminated than the other end of the bar code, the nonreflective areas in the intensely illuminated end may reflect more light than the reflective areas in the less intensely illuminated end of the bar code. The processor will likely be unable to read the bar code because it will not be able to distinguish the non reflective surfaces from the reflective surfaces.
Bar codes, as described above, are sometimes used in autochangers. An autochanger is a device that stores media pieces in a library and moves selected media pieces from the library to a media player when a user requests information stored on the selected media pieces. Likewise, when the user no longer requires the information on a selected media piece, the autochanger moves the media piece from the media player to a specific location in the library. The autochanger uses a media handling device, sometimes referred to herein as a picker, to move selected media pieces between the library and the media players. Bar codes may be affixed to the media pieces and may serve to identify contents of the media pieces. A bar code reader, as described above, may be affixed to the picker and may serve to read the bar codes affixed to the media pieces.
Two objectives in the design of an autochanger are to minimize human involvement required in the operation of the autochanger and to maximize the space available in the autochanger for media storage. Minimizing human involvement required in the operation of the autochanger may, in part, be achieved by the use of bar codes affixed to the media pieces as described above. The autochanger, rather than a human user, may read the bar codes to determine the contents of the media pieces and the locations of the media pieces within the autochanger. The user, thus, only needs to place the media pieces into the library. This minimizes human involvement in the operation of the autochanger and reduces the probability of errors in identifying the contents and locations of the media pieces.
Maximizing the space available for media storage within an autochanger may be achieved, in part, by reducing the amount movement required by the picker, minimizing the size of the components comprising the autochanger, and integrating the components comprising the autochanger into single packages. Reducing the picker movement increases the space available for media storage because media pieces are not able to be stored in the space dedicated to picker movement. Integrating the components comprising the autochanger generally decreases the number of components comprising the autochanger and, thus, increases the space available for media storage. One example of maximizing the space available for media storage in the autochanger is to minimize the size of the bar code reader and to integrate the bar code reader into the picker.
Integrating the bar code reader into the picker presents several problems. Several other components may also be located within the picker, which constricts the space available for the illuminator and the imaging device. These other components may interfere with the light beams associated with the illuminator and the imaging device. The picker may have to be enlarged to accommodate the illuminator and the imaging device, however, this defeats the purpose of minimizing the sizes of the components comprising the autochanger. Another problem with locating the illuminator and the imaging device within the picker is that their light beams must be aligned to intersect at a point external to the picker where a bar code will be located. This alignment is difficult to perform within the tight confines of the picker. A third problem with locating the bar code reader within the picker is that the picker may have to move an extra distance in order for the bar code reader located within the picker to be properly positioned to read a bar code. This extra movement requires space within the autochanger to be dedicated to picker movement rather than to media storage.
Therefore, a need exists for a bar code reader that is able to be located within a picker of an autochanger wherein the picker is neither required to be enlarged to accommodate the bar code reader nor move an extra distance in order for the bar code reader to read a bar code.
An improved optical assembly is disclosed herein. The improved optical assembly comprises an optical device associated with a lens wherein the lens has an optical axis. The improved optical assembly further comprises a light path extending between a point and the optical device wherein the light path passes through the lens. The light path may be steered to intersect an object by spacing the optical device a distance from the optical axis of the lens.
The improved optical assembly may be used in a bar code reader application. A first optical assembly may be an illuminator in which the lens is and illuminating lens and the optical device is a light source. An illumination beam generated by the light source may be steered to intersect a bar code by spacing the light source a distance from the optical axis of the illuminating lens. A second optical assembly may be an imaging device in which the lens is an imaging lens and the optical device is a photosensor. An image beam associated with the photosensor may be steered to intersect the bar code by spacing the photosensor a distance from the optical axis of the imaging lens.
The improved optical assembly allows the optical devices to be mounted to a single printed circuit board, which may further reduce the size of the device that uses the optical assembly. In a conventional optical assembly, the optical devices cannot be mounted to the same printed circuit board because their light beams would extend parallel and, thus, would not intersect at a point. The optical devices used in the optical assembly disclosed herein may be located on the same printed circuit board by spacing the optical axes of the lenses appropriate distances from the optical devices so that the light beams intersect a common point. This application may be used in a bar code reader so that the light source and the photosensor may be mounted to the same printed circuit board. The illumination beam and the image beam may then be steered to intersect a bar code.
This bar code reader with the illuminator and photosensor mounted to the same printed circuit board may be used in a picker of the type used in an autochanger. The bar code reader is able to fit within the tight confines of the picker by steering the illumination beam and the image beam so as to avoid the other components located within the picker. Additionally, the bar code reader only requires minimal alignment to steer the light beams to intersect a bar code because the illuminator and the imaging device are integrated together within the picker.